Control



W. DOBLE Sept. 19, 1933.

CONTROL Filed .A rii 24, 1931 %%W TO M m H mm w r A f NM mm Patented Sept. 19, 1933 UNITED'QSTA res PATENT OFFICE common Warren Doble, Berkeley, Calif. I Application April 24, 1931; Serial No. 532,514

Claims. (01. 122-448) My invention relates primarily to'means for controlling the operation of vaporgenerators such as steam boilers and relates particularly to the control of boilers of the forced circulation.

5 type. Such-boilers usually comprise a tube several hundred feet. in length which is subjected to heat and through which a current of feed fluid is forced. Such units find particular application in automotive practice especially in -automobiles.

of the issuing vapor substantially constant.

despite wide fluctuations in the load on the boiler or the quantity of the vapor supplied thereby.

A device of thisgeneral character is disclosed in the application of William J. Besler, entitled Control filed April 24, 1931 with Serial Number 532,511. In the arrangement shown in the Besler application there is provided for-the control of the boiler a means for introducing feed fluid into the primary inlet or foot of the boiler tube together with a branch for supplying feed fiuid between the ends of the boiler coil or tube. Although the pressure of the vapor issuing from a boiler of this character is usually'reg'ulated so that it does not exceed a predetermined maximum value nevertheless,- due to various degrees of throttle opening and due to. the generaloperation of the system, the pressure within the boiler tube may fluctuate or vary from oneend to the other end. Such \fluctuations are particularly pronounced in automotive practice where the throttle valve is opened and shut rapidly and bei tween very wide limits. In one practical installation although the outlet steam is regulated not to exceed 1500 pounds persquare inch pressure the outlet pressuremay drop below this value as -much as five or six hundred poundspersquare' inch. The pressure, however, at the inlet end of the boiler does not vary appreciably so that the pressure drop throughout the length of the boiler tube may varyfrom substantially nothing when the throttle isv closed to a value of the order of 500 pounds per square inch. 59 An objectof my invention is to provide a'control for a boiler so that the temperature of the steam or vapor issuing from the boiler issubstantially constant.

. Another object of my invention is to provide a control for a boiler suchthat fluctuations in pressure drop through the boiler have substantially no adverse efi'ect upon the control system.

The foregoing and other objects are attained in the embodiment of the invention shown in the drawing, in which The figure is a, diagrammatic showing of a control constructed in accordance with my invention.

In its preferred form, the control of my invention comprises a boiler tube'which is subjected to heat and which has a primary inlet at one end thereof and a secondary inlet between the ends thereof together with means for forcing feed fluid into the primary inlet and into the secondary inlet, the flow into the secondary inlet being under control of a mechanism for establishing'substantially a constant flow into the secondary inlet.

In the form of my invention illustrated in the drawing, there is provided a vapor generatoror boiler generally designated 6 which includes a casing 17 within which a boiler tube 8 is situated. The tube is relatively long and is preferably coiled into a plurality of convolutions so that it occupies a major amount of space within the casing 7. The tube 8 at its foot 9 is provided with a primary inlet 11 and at its opposite end affords an outlet 12 which is controlled by a throttle 'valve 13in the customary fashion. In order that the boiler tube 8 can be heated, the casing 7 is intersected by a venturi 14.into which an air blower 16 discharges. The blower is preferably driven by an electric motor '17 and/or other suitable source pf power and induces a current of air to flow through the venturi 14 wherein fuel from a carburetor 18 is aspirated and the resulting mixture is discharged into the combustion space 19 of the boiler 6. The mixture is preferably ignited by a standard spark plug 20.

In order to supplythe boiler coil 8 with feed fluid there is provided a. source of fluid, such as conditions such, for instance, as steam pressure,

steam temperature, boiler tube temperatures, etc, .the outlet 12 is preferably joined by a pipe 33 to a pressure cell 34. The pressure cell 34 is adjusted to respond to a predetermined pressure and upon attainment of this pressure causes a lever 36 to move a contact 3'7 away from a stapump 23.

tionary contact 38. The contact 3'7 is connected by, a wire 39 through a master switch 41 to one side of a source of electromotive force, such as a battery 42, the other side of which is grounded as at 43. The contact 38 is connected by a lead 44 and a flexible wire 46 to a movable contact 47 carried on a rocker 48. The rocker 48 is preferably responsive to aboiler condition such as tube temperature and to this end I preferably provide a thermostat 49 in thermal relation to the boiler tube 8 adjacent the outlet 12 thereof. When the temperature of the thermostat 49 is relatively low the contact 4'7 is in abutment with a contact 51 connected by a lead 52 to the motor 1'7, the other terminal of which is grounded by a wire 53. Simultaneous energization of the spark plug 20 is obtained by a wire 56 extending to an induction coil 5'7 of the usual kind.

Whenever the boiler tube 8 is below a predeterminedtemperature and the master switch 41 is closed then, if the pressure is below its prede-. termined value, the contacts 3'7 and 38 are'in abutment and the contacts 4'7 and 51 are in abutment so that the electric motor 17 is energized thereby compelling a combustible mixture to become ignited by the spark plug 20 and to burn within the combustion space 19 so that the boiler tube 8 is heated. The products of combustion are discharged through an outlet 61.

When the temperature of the boiler tube arrives. at a predetermined value the thermostat 49 expands and rocks the rocker arm 48 so that contacts 62 and 63 are closed. The contact 62 is connected by a lead 64 to the'conductor 44 while the contact 63 ,is connected by a wire 66 to an electromagnet orso1enoid'67 the other terminal of which is connected to ground by a lead 68. The electromagnet controls a valve 69 governing communicationthrough the duct 26. When the contacts 62 and 63 are closed the electromagnet 6'7 is energized thereby opening the valve 69 and permitting vapor to flow through the duct 26 and to drive the engine 24. The pump 23 is thereby operated and withdraws water from the tank 21 and introduces it through the primary inlet 11 into the boiler tube 8. If the introduction of such feed fluid reduces the temperature of the thermostat 49 or if for any reason the temperature of the thermostat 49 drops below the predetermined value, the contacts 62 and 63 are again opened interrupting the operation of the If the temperature of the thermostat increases materially above the predetermined temperature despite the operation of the contacts 62 and 63, the contacts 4'7 and 51 are opened thereby interrupting the supply of heat to the tube by deenergizing the electric driving motor 1'7 and stopping operation of the blower 16.

In practice the contacts 62 and 63' and the contacts 4'7 and 51 are so adjusted that the contacts 62 and 63 abut at a temperature slightly below that at which the contacts 4'7 and 51 separate. Under any conditions where the pressure within the boiler tube exceeds the predetermined valuefor which the pressure cell 34 is adjusted, the lever 36 is pivoted to break or separate the contacts 3'7 and 38 thereby interrupting operation of the blower 1'7 and the pump 23.

Inasmuch as the feed fluid which is introduced through the foot of the boiler 9 must traverse the entire length or substantially the entire length of the boiler tube 8 before it can affect the thermostat 49 and since in practice this distance is often of the order of several hundred feet, in one practical example being approximately six hundred feet, the time lag is so great as to be objectionable. The flow of feed fluid through this length of boiler tube is also materially aifected by virtueof the fact that when the throttle 13 is closed or substantially closed, the pressure at the foot or primary inlet 11 of the boiler is substantially the same as the pressure proximate the outlet 12 thereof. However, when the throttle 13 is opened a material amount, the pressure adjacent the outlet 12 is much less than the pressure adjacent the primary inlet 11; in certain cases this pressure drop amounts to approximately five hundred pounds per square inch. Such a pressure drop causes a very rapid flow of fluid through the boiler tube 8 but since the pressure drop fluctuates, the rapidity of flow cannot be depended upon and even at its best the flow is not sufficiently fast to affect the thermostat 49 as quickly as desired to insure a substantially constant temperature of steam leaving the outlet 12.

In order to overcome the time lag involved and in order to improve the regulation or constant temperature characteristics of the boiler I preferably join the duct 31 and the boiler tube 8 at a point between the thermostat 49 and the primary inlet 11 but preferably close to the thermostat 49. To this end a branch conduit '71 intersects the duct 31 and also intersects the boiler tube 8 at a secondary inlet '72 almost immediately in advance of the thermostat 49. Preferably the branch conduit '71 is provided with a check valve '73 to prevent return flow therethrough.

Although in practice I prefer that the proportion of feed fluid flowing through the branch conduit '71 into the secondary inlet '72 bear a relatively fixed relationship to the proportion of feed fluid flowing through the primary inlet 11 such a proportion is relatively difficult to maintain primarilyon account of the wide fluctuation in pressure drop through the boiler tube from the primary inlet 11 thereof to the outlet 12 thereof. In order to maintain a substantially constant rate of flow through the branch conduit '71 into the secondary inlet '72 whenever the pump 23 is operating, I preferably interpose in the branch conduit '71 a flow regulating mechanism generally designated '74. This mechanism preferably includes an enlarged cylindrical chamber '76 having an inlet '77 at one end communicating with the branch conduit '11 and having at the other end an outlet tube '78 which extends into the cylindrical chamber and provides a seat therein.- Adapted to reciprocate within the cylindrical chamber between two extreme positions is a piston '79. This piston in one extreme position is adapted to seat on the outlet tube '78 and prevent flow therethrough thereby stopping all flow through the branch conduit '71 into the one end of the cylindrical chamber and the piston 79. Since the piston '79 on one face is subjected to pressure due to the pump 23 and on the other face is subjected to pressure existing within the boiler tube 8 proximate the secondary inlet '12, such pressure difference as may exist is rendered ineif'ective to vary the flow through the branch conduit 71 by virtue of the aperture 81 and the spring 82. Whenever the flow through the aperture 81 tends to increase due to an excessive pressure on the pump side of the piston 79 the piston is driven against the urgency of the spring 82 toward the seat on the outlet tube 78 thereby restricting or preventing flow through the outlet tube. The restriction of flow through the branch conduit 71 is then inversely equivalent to the increased pressure. drop. When the pressure in the tube 78 again rises, the piston is driven away from the seat on the inlet tube 78 under the urgency of the spring 82. Due to the operation of the piston alternately approaching and receding from the seat on the tube 78 as the pressure drop through the tube 8 fluctuates, the flow through the branch conduit '71 is maintained substantially constant or at a substantially fixed'rate despite the pressure drop through the boiler tube 8 and despite any fluctuations in such pressure drop. The amount or quantity per unit of time or the rate of flow of feed fluid introduced through the secondary inlet 72 whenever the pump 23 operates is thereby made substantially constant despite fluctuations in the pressure drop through the tube 8 and the resulting temperature of the vapor or steam issuing from the boiler tube outlet 12 is held within very close limits.

It is to be understood that I do not limit myself to the form of the control shown and described herein, as the invention, as set forth in the following claims may be embodied in a plurality of forms.

I claim:

1. A control comprising a boiler tube, means for heating said tube, means for introducing feed. fluid into one end of said tube, means for introducing feed fluid into said tube between the ends thereof, and means responsive to pressure differential between the points of introduction of said feed fluid for regulating the quantity of feed fluid introduced by said second introducing means.

2. A control comprising a boiler tube, means for heating said tube, means for introducing feed fluid into one end of said tube, a conduit intersecting said tube between the ends thereof, means for causing feed fluid to flow through said conduit into said tube, and means responsive to pressure differential between the points of entry of feed fluid to said tube for regulating said flow through said conduit.

3. A control comprising a'boiler tube, means for heating said tube, means for introducing feed fluid into one end of said tube, a conduit intersecting said tube between the ends thereof, means for causing feed fluid to flow intermittently through said conduit into said tube, and means for establishing the rate of said flow at a constant value.

' 4. A control comprising a boiler tube having a primar inlet and a secondary inlet, the pressure in sai tube fluctuating between said primary inlet and said secondary inlet, means for introducing feed fluid into said tube through said primary inlet, and means for introducing feed fluid into said tube through said secondary inlet at substantially aconstant rate despite fluctuating pressure.

5. A control comprising a boiler tube having a primary inlet and a secondary inlet, a feed fluid pump, a conduit extending from said pump to said primary inlet, a branch conduit extending from said conduit to said secondary inlet, and means in said branch conduit for regulating fluid passing therethrough in response to pressure differential between said primary inlet and said secondary inlet.

6. A control comprising a cylindrical chamber, an outlet tube extending into said chamber to provide a seat, an inlet communicating with said chamber, a piston reciprocable in said chamber and adapted to abut said seat, said piston having an aperture therethrough out of communication with said outlet tube when said piston abuts said seat, and a spring for biasing said piston away from said seat.

7. A control comprising a cylindrical chamber having an inlet passage at one end thereof and an outlet passage at the other end thereof, a piston reciprocable in said chamber between two extreme positions, said piston being apertured to afford communication between opposite sides thereof and being adapted in one of said extreme positions to close said outlet passage, and a spring for urging said piston toward the other of said extreme positions.

8.. A control comprising a boiler tube having a primary feed fluid inlet and a secondary feed fluid inlet, there being a variable pressure difference in said tube between said inlets, means for introducing feed fluid into said tube through said secondary inlet, and means for regulating the introduction of said feed fluid in response to said pressure difference.

9. A control for a forced circulation boiler having a primary feed fluid inlet and having a secondary feed fluid inlet comprising a duct of variable cross section for conducting feed fluid to said secondary inlet, and means for varying the cross section of said duct in accordance with the pressure drop through said boiler between said primary inlet and said secondary inlet.

10. A control for a forced circulation boiler having a primary feed fluid inlet and having a secondary feed fluid inlet comprising a duct of variable cross section for conducting feed fluid to said secondary inlet, and means for varying the cross section of said duct in inverse proportion to the pressure drop through said boiler between said primary inlet and said secondary inlet.

WARREN DOBLE. 

